Submitted to: Annual Reviews of Plant Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/11/2001
Publication Date: 6/1/2003
Citation: MOONEY, B.P., MIERNYK, J.A., RANDALL, D.D. THE COMPLEX FATE OF ALPHA-KETOACIDS. ANNUAL REVIEWS OF PLANT BIOLOGY. 2002. v. 53. p. 357-375. Interpretive Summary: Respiration is the use of energy by living cells to do work. Both growth and reproduction are directly coupled to rates of respiration. As a result, respiration must be carefully controlled or wasted energy would decrease crop yields and reduce agricultural productivity. The control of respiration in plant cells is a subject of ongoing study. A family of proteins, the alpha-ketoacid dehydrogenase complexes, are critical to the control of respiration. The structures of the four types of complexes is compared from an evolutionary perspective to try to better understand how the different control mechanisms arose. A digital analysis of the expression of each of the protein components of each complex was performed to test the possibility that control of gene expression is a significant factor in the overall control mechanism. This information will be important to researchers in their attempts to increase agricultural productivity by altering the control of plant cell respiration, and to other plant scientists who will try to design more efficient crop plants through either classical breeding or biotechnology.
Technical Abstract: Plant cells are unique in that they contain four species of alpha-ketoacid dehydrogenase complex: plastidial pyruvate dehydrogenase, mitochondrial pyruvate dehydrogenase, alpha-ketoglutarate (2-oxoglutarate) dehydrogenase, and branched-chain alpha-ketoacid dehydrogenase. All complexes include multiple copies of three components: an alpha-ketoacid dehydrogenase/ decarboxylase, a dihydrolipoyl acyltransferase, and a dihydrolipoyl dehydrogenase. The mitochondrial pyruvate dehydrogenase complex additionally includes intrinsic regulatory protein-kinase and -phosphatase enzymes. The acyltransferases form the intricate geometric core structures of the complexes. Substrate channeling plus active-site coupling combine to greatly enhance the catalytic efficiency of these complexes. These alpha-ketoacid dehydrogenase complexes occupy key positions in intermediary metabolism, and a basic understanding of their properties is critical to genetic and metabolic engineering. The current status of knowledge of the biochemical, regulatory, structural, genomic, and evolutionary aspects of these fascinating multienzyme complexes are described in detail.